The present invention relates to an overload protection system for a sensing head of the type used with measuring or processing machines, in which the sensing head comprises a sensing head casing and a mandrel is used for mounting the sensing head to the measuring or processing machine.
A wide variety of mechanical zero sensing arrangements are known for machine tools (German DE-OS No. 15 48 326) and for measuring and testing instruments (German Patent DE-PS No. 10 28 792) which are provided with a spring type overload protection arrangement.
Furthermore, sensing heads are known for multicoordinate measuring or processing machines in which the deflection of a sensing pin by contact with a workpiece triggers an electrical signal (German DE-AS No. 19 32 010 and British Pat. No. 1,599,758). The sensing pins of the sensing heads described in these two documents assume a rest position automatically, which is extremely exactly defined as a zero position. For many applications the sensing pin must return to the zero position after deflection with an accuracy of 1 micron, since many measuring processes are numerically controlled, and therefore must operate automatically. Typically, an adjustment of the scanning pin is therefore not provided in such sensing heads.
Such sensing heads can be relatively expensive components, and therefore correspondingly high costs arise when the sensing pin of the sensing head is damaged due to excessive deflection of the sensing pin.